1. Field of the Invention
The disclosed invention relates generally to photoconductors. Particularly, the invention is directed to a photoconductor detector that is suitable for use in sensor systems that require large numbers of very small detectors for high resolution.
In a sufficiently small photoconductor detector, where the length between metallic contacts is less than the minority carrier diffusion length, the detectivity of the detector decreases with the length between metallic contacts.
2. Description of the Prior Art
The prior art includes detectors wherein the metallic contacts are deposited on the semiconductor material at the boundary of the detector region. Thus, the length between metallic contacts is the length of the detector region.
An improvement of the foregoing structure utilized extended contacts wherein the length between metallic contacts (as measured where the contacts are deposited on the semiconductor material) is increased by extending the contacts away from the detector region. In the extended region the contacts are insulated from the semiconductor material. Thus, the metal mask extends to the boundary of the detector region and the optical length of the detector region is preserved. The extended contact geometric, is disclosed in Kinch et al., Geometrical Enhancement of HgCdTe Photoconductive Detectors, Infrared Physics, 1977, Vol. 17, pp. 137-145.
Although the extended contact photoconductor provided increased detectivity, it was limited. Moreover, the prior art photoconductors did not have sufficient injection efficiency when used with current mode preamplifiers because of high contact impedance.